1. Field of the Invention
The present invention relates to the field of angioplasty. In particular, the present invention relates to an apparatus and method for facilitating the exchange of a dilatation balloon catheter on a guide wire.
2. Description of the Prior Art
Angioplasty has gained wide acceptance in recent years as an efficient and effective method for treating types of vascular diseases. In particular, angioplasty is widely used for opening stenoses in the coronary arteries, although it is also used for treatment of stenoses in other parts of the vascular system.
The most widely used form of angioplasty makes use of a dilatation catheter which has an inflatable balloon at its distal end. Using fluoroscopy, the physician guides the catheter through the vascular system until the balloon is positioned across the stenosis. The balloon is then inflated by supplying a fluid under pressure through an inflation lumen to the balloon. The inflation of the balloon causes stretching of the artery and pressing of the lesion into the artery wall to re-establish acceptable blood flow through the artery.
Two types of dilatation catheters are "over-the-wire"catheters and "non-over-the-wire" catheters. An over-the-wire catheter is one in which a separate guide wire lumen (sometimes called a "thru lumen") is provided so that a guide wire can be used to establish a path through the stenosis. The dilatation catheter is then advanced over the guide wire until the balloon is positioned across the stenosis. One problem with the over-the-wire catheter is the inability to maintain the position of the guide wire within the vascular system when removing the catheter, and when exchanging it for one of a smaller (or larger) balloon diameter.
It is desirable to maintain the position of the guide wire across the stenosis during the exchange of catheters to ensure the safety and speed of the angioplasty procedure. Attempts to alleviate the problem of guide wire movement include the use of long or "exchangeable"guide wires, or extendable guide wires. These guide wires are of a length such that a proximal portion of the guide wire extends outside the patient's body while a distal portion of the guide wire passes through the body and across the stenosis. Thus, during an exchange of balloon catheters on the wire, the guide wire position across the stenosis is maintained by holding onto a proximal segment of the guide wire from outside of the body. However, guide wire movement relative to the stenosis still occurs despite such external fixation of the guide wire. These guide wires also have the disadvantage of being cumbersome and difficult to handle while maintaining the guide wire position across the stenosis. For example, a length of guide wire of approximately 150 cm must be maintained outside the body (either by an extension or by a 300 cm long base guide wire). Furthermore, x-ray fluoroscopy must be used during the exchange in order for the operator to see the wire being held in position across the stenosis. This use of fluoroscopy results in an undesirable, excessive exposure of x-ray radiation to the patient and also to the attendant medical personnel.
A non-over-the-wire catheter (also called a "fixed wire"catheter) acts as its own guide wire, so that the exchange of catheters necessarily requires removal of the catheter/guide wire assembly from the stenosis area. Thus, when accomplishing an exchange with the "non-over-the-wire"catheter, the path to the stenosis must be re-established when replacing the catheter with one having a different balloon diameter.
In both types of catheter/guide wire systems, it is difficult to effectively maintain or realign the guide wire across the stenosis. In addition, the exchange often requires more than one person to perform the procedure and requires extensive use of fluoroscopy resulting in excessive x-ray exposure to the patient.